1. Field of the Invention
The present invention relates to a side impact protection airbag system in which when an impact is applied to a vehicle from an outside thereof, an airbag is inflated to be deployed in the vicinity of an outer side of an occupant seated in a vehicle seat so as to restrain the occupant for protection of the occupant from the impact so applied.
2. Related Art
When a vehicle is involved in a sideways collision, a side impact protection airbag system or simply a side airbag system is known as a system for protecting an occupant from an impact which is applied to a body side portion of a vehicle such as a side door from an outer side as a result of the collision. The side airbag system is made up of an inflator, a retainer and an airbag. The inflator has a substantially cylindrical gas ejecting part, and a plurality of gas ejecting holes are provided along substantially the full circumference of an outer circumferential surface of the gas ejecting part, whereby an inflation gas is made to be ejected from the gas ejecting holes in response to an impact applied from an outer side of a vehicle as a result of the vehicle being involved in a sideways collision. The retainer has a tubular wall part which holds the inflator to cover it from an outside. An opening for permitting a passage of at least part of the inflation gas from the gas ejecting part is provided in the wall part in a position lying in the vicinity of the gas ejecting portion.
In addition, when protection objects by the side airbag system includes the pelvis and chest of an occupant, the constituent members (the inflator, retainer and airbag) are accommodated in an external portion of a seatback (a back resting portion) of a vehicle seat. The airbag is fixed to a seat frame within the seatback together with the inflator and the retainer at one end portion (a fixing end portion) thereof.
In the side airbag system, when an impact is applied to the body side portion as a result of the vehicle being involved in a sideways collision, an inflation gas is ejected from the gas ejecting part of the inflator and is then supplied into the airbag. When the inflation gas is supplied thereinto, the airbag projects forwards from the seatback with its fixing end portion left fixed in place in the seatback, passes through a gap defined between the occupant seated in the vehicle seat and the body side portion and is inflated to be deployed into a size and shape which can protect the side portion (the pelvis and chest) of the occupant. The occupant is restrained by the airbag so deployed and the impact that is transmitted to the occupant from the outside through the body side portion is relaxed.
Here, speaking of the resistance to impact of the side part of the human body, it is generally known that the pelvis is superior to a portion lying thereabove, for example, the chest. Because of this, the impact acting on the occupant desirably becomes smaller at the chest than at the pelvis by the inflation and deployment of the airbag.
To make this happen, for example, JP-A-2005-178470 describes a side impact protection airbag system in which an interior space of an airbag is divided into a first chamber and a second chamber lying thereabove by providing a dividing part through sewing, so that an inflation gas ejected from an inflator is distributed more into the first chamber than into the second chamber. In this side airbag system, a gas ejecting part and an opening are provided between a fixing end portion of the airbag and an end portion of the dividing part which lies on a side facing the fixing end portion of the airbag.
According to the side airbag system, the first chamber is inflated and deployed at a higher internal pressure in the vicinity of an outer side of the pelvis having the higher resistance to impact at the side portion of the occupant, while the second chamber is inflated and deployed at a lower internal pressure than the first chamber in the vicinity of an outer side of the chest having the low resistance to impact. In this way, the airbag is inflated and deployed in the pressure distribution which matches the resistance to impact of the side portion of the occupant, whereby the respective body portions of the occupant is protected effectively from the impact resulting from the sideways collision.
Incidentally, in addition to JP-A-2005-178470 that has been described above, JP-A-2005-170362 also describes a retainer of an airbag system. In either of the retainers, the opening is made to open forwards in the deploying direction of the airbag. The one end portion (which lies on the side facing the fixing end portion of the airbag) of the dividing part is positioned in the vicinity of the front of the opening in the deploying direction of the airbag. Because of this, there is a fear that the inflation gas, which is ejected from the gas ejecting part of the inflator, passes through the opening in the retainer and is then forcibly ejected forwards in the deploying direction of the airbag, is caused to strike directly the end portion of the dividing part which was made through sewing to thereby damage the end portion in question.
Consequently, in order to suppress the damage to the dividing part by the inflation gas, countermeasures such as covering the gas ejecting part with an inner tube or reinforcing the dividing part with a reinforcement fabric need to be taken separately.
In addition, this problem can equally occur on a so-called “curtain shield” airbag system in which an airbag is accommodated in a roof side rail near a door to be inflated and deployed between the head of an occupant and a window in the door in response to an impact that is applied from an outer side of a vehicle when the vehicle is involved in a sideways collision, an interior space of the airbag being divided into a plurality of chambers by a dividing part.